primitive knot

DMZ

Organizer for gastrulation in vertebrates. The primitive knot starts as a regional knot of cells that forms on the blastodisc immediately anterior to where the outer layer of cells will begin to migrate inwards - an area known as the primitive streak. Posterior to the node is the primitive pit, where the cells of the epiblast (the upper layer of embryonic cells) initially begin to invaginate. This invagination expands posteriorly into the primitive groove as the cells layers continue to move into the space between the embryonic cells and the yolk. This differentiates the embryo into the germ layers - endoderm, mesoderm, and ectoderm. The primitive knot migrates posteriorly as gastrulation proceeds, eventually being absorbed into the tail bud.[WP]. the regional thickening of cells at the rostral tip of the vertebrate primitive streak through which gastrulating cells migrate anteriorally to form tissues in the future head and neck; this region organizes the formation of the three embryonic layers and establishes the longitudinal axis and the polarity of the embryo[MP].

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类型 Bone
上级结构 embryonic structure
拉丁名称 DMZ
FMA ID 293116

Frequently Asked Questions

What is the primitive knot?

The primitive knot (also called Hensen's node or the organizer) is a specialized group of cells at the anterior end of the primitive streak in the developing embryo. It acts as the primary organizer of gastrulation and body axis formation in vertebrates.

What is the function of the primitive knot?

The primitive knot organizes gastrulation by directing the migration of epiblast cells through the node and along the primitive streak. It secretes signaling molecules that establish the body axes (anterior-posterior, dorsal-ventral) and induces neural tube formation.

Where does the primitive knot form in the embryo?

The primitive knot forms at the anterior (cranial) end of the primitive streak on the blastodisc (embryonic disc). In human development, this occurs during the third week of embryogenesis.

What key signaling molecules are secreted by the primitive knot?

The primitive knot secretes important signaling molecules including chordin, noggin, and follistatin (which antagonize BMP signals to induce neural tissue), as well as sonic hedgehog (Shh) and Wnt pathway inhibitors that pattern the embryonic axes.

What structures are derived from cells passing through the primitive knot?

Cells ingressing through the primitive knot form the prechordal plate (contributes to cranial mesoderm and future head structures) and the notochord, which induces overlying ectoderm to form the neural plate and subsequently the neural tube.

References

  1. Foundational Model of Anatomy — FMA:293116 Reference anatomy ontology (University of Washington)
  2. UBERON — UBERON:0003062 Cross-species anatomy ontology (EMBL-EBI Ontology Lookup Service)

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Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.